North-east Scotland ruled out as source of Stonehenge Altar Stone

Researchers have ruled out north-east Scotland as the source of Stonehenge’s six-tonne Altar Stone, renewing the mystery of where the distinctive sandstone slab came from.

The 4.9-metre stone, now mostly buried within the monument, was once thought to have come from Wales. A previous study instead pointed to north-east Scotland, but geological tests in the Orcadian Basin found no location with matching characteristics.

The latest investigation combined new observations with analysis of museum fragments, examining the stone’s structure, minerals and composition. It has been published in the Journal of the Geological Society.

Study lead Professor Duncan Pirrie, of the University of South Wales, said the work left researchers “far better equipped to focus on the areas most likely to yield an answer”. He described it as the most comprehensive geological investigation of the stone so far.

Nick Pearce, a geochemistry expert at Aberystwyth University who worked on the earlier research, said eliminating possible source areas was as important as identifying new ones. The Altar Stone is unique among Stonehenge’s stones, and finding its origin could shed light on how it reached Salisbury Plain thousands of years ago.

Stonehenge was built in several phases between 3000 and 1600 BC. Some of its smaller bluestones came from west Wales, about 225km away, but the Altar Stone’s source remains unknown.